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### Course: 5th grade > Unit 16

Lesson 3: Properties of shapes# Polygons review

Review the term polygon and name polygons with up to 8 sides. Then, try some practice problems.

## What is a polygon?

A polygon is a closed figure with at least $3$ straight sides.

## Practice set 1

*Want to learn more about recognizing shapes? Check out this video.*

## Identifying polygons

Polygons can be named by their number of sides.

Number of sides | Name |
---|---|

Triangle | |

Quadrilateral | |

Pentagon | |

Hexagon | |

Heptagon | |

Octagon |

### Practice set 2

*Want to try more problems like this? Check out this exercise*

## Want to join the conversation?

- I have learned about Geometry basic here, then I want to curious how many polygons or shape in the world at all ? only till to 8 (Octagon) or is there more polygons ?(96 votes)
- There are many more! 9 sides? Nonagon, 10 sides? Decagon. And so on and so on until there are so many sides you could hardly tell the difference between them and circles.(119 votes)

- What is a 24-sided shape called?(49 votes)
- A icositetragon

An icosogon is 20 sides, and tetra means 4.

Put them together and you get 24(76 votes)

- What is the difference between a circle, an ellipse, and an oval?(25 votes)
- The difference is; with a circle the diameter IS THE SAME all the way around, but with a ellipse the diameter CAN CHANGE as you go around, so a circle is a ellipse but an ellipse is not always a circle. Hope this helps!(56 votes)

- What's a polygon(28 votes)
- 1）A polygon is a shape that has STRAIGHT sides.

2）They MUST have sides that are closed.

3）They also NEED to have at least three sides.

4）They have the same number of sides and angles.

According to 3 and 4, a circle does not count(20 votes)

- What are the names for the polygons above octagon?(27 votes)
- 9--Nonagon

10--Decagon

11--Hendecagon

12--Dodecagon(41 votes)

- Are quadrilaterals always four sided shapes?(24 votes)
- Yes they are always four sided.(35 votes)

- why does every shape have gon at the end, like hexagon or a pentagon ect.(23 votes)
- -Gon is a suffix for a shape that has a specific number of angles.(33 votes)

- Who invented the word polygon?(19 votes)
- The Greeks invented the word "polygon" probably used by the Greeks well before Euclid wrote one of the primary books on geometry around 300 B.C.

"polygon" has been used in English since around 1560

The word comes from two parts:

"poly-" = many

"-gon" = angle (or knee)(32 votes)

- Why is squares rectangles,but rectangles is not squares?Explain(18 votes)
- A rectangle has four sides and four right angles, which can also be said about squares.

However, a square has four*equal*sides, which can not be said about all rectangles.(25 votes)

- So, is a five-sided shape a quadrilateral?(1 vote)
- No, 4 sided shapes are quadrilaterals

5 sided shape is a pentagon(34 votes)